Rocky Mountain snowpack changes and their hydrologic consequences during the Holocene

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Loss of high-elevation snowpack in the intermountain western US poses major societal risks for the region, where increased temperatures may permanently reduce snowpack amounts and impact baseflow in rivers and streams. This research looks towards the geological record of past climates recorded by proxy in organic sediments in lakes and uses this information to provide a perspective on how future water resources in the region will respond to climate change. The past records of the water cycle provide this long-term context to recent changes by analyzing the combinations of temperature and precipitation changes that have impacted snowpack in the past. Such reconstructions can help anticipate future changes. The results of this research will be communicated to broad audiences of stakeholders from public agencies to residents of the region. The research team will work with the University of Wyoming Geology Museum and media outlets, such as Wyoming Public Radio, to present the results through interviews and media. Research and education capacity will be built at the University of Wyoming and at a long-term monitoring site maintained by the US Forest Service.This project will use a novel combination of lake sediment biomarker and mineral analyses to constrain the changes in snowpack, temperature, runoff, evaporation, and dust deposition over the past 11,000 years in three small Rocky Mountain watersheds that are sensitive to climate change. Specifically, the research will develop three new C29 n-alkane (leaf wax) and C23 n-alkane (aquatic) hydrogen isotope records, along with three x-ray diffraction records of lake sediment mineralogy, and three comparable branched GDGT (glycerol dialkyl glycerol tetraether) records of lake water temperature. The combination of these proxies will provide a multi-proxy perspective on changes in Rocky Mountain snowpack, and use to assess climatological and hydrological factors involved in the proxy records. In so doing, the combination of these different types of data will enrich the understanding of the variability of water resources in the western US and the mechanisms underlying these changes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.